Harmothoe benthaliana McIntosh, 1885

Barnich, Ruth & Fiege, Dieter, 2009, Revision of the genus Harmothoe Kinberg, 1856 (Polychaeta: Polynoidae) in the Northeast Atlantic, Zootaxa 2104 (1), pp. 1-76 : 26-28

Harmothoe benthaliana McIntosh, 1885

( Figs. 4 ; 12A–E )

Harmothoe benthaliana McIntosh, 1885: 95 , pl. 13 fig. 3, pl. 20 fig. 7, pl. 10A figs. 9–10.

Harmothoe joubini Fauvel, 1913: 15 , fig. 5; Fauvel (1914a): 54, pl. 3 figs. 6–12 [new synonymy].

Harmothoe joubini rosaurae Monro, 1939: 350 , textfig. 281 [new synonymy].

Type material. Harmothoe benthaliana : 2 syntypes, BMNH 1885.12 .1.75, "Challenger" St. 45, off the American coast, 38°34'N 72°10'W, 3 May 1873, dredged, 1240 fms, blue mud .

Harmothoe joubini : 2 syntypes, IEA I/30 (slides with fragments), Campagne scientifique d’Albert Ier 1902, St. 1269, 60 miles SSE off Cape Saint Vincent, Portugal, 1473 m, mud .

Harmothoe joubini rosaurae : 4 syntypes (2 cs, 2 af), BMNH 1941.1.1.16–19, "Rosaura" St. 49, between Fuerteventura and Africa, 28°25’N 13°34’W, Agassiz trawl, 1300 m .

Diagnosis. Anterior pair of eyes dorsolateral at widest part of prostomium. Elytral margin smooth; conical microtubercles in a patch near anterior margin. Noto- and neurochaetae with faint rows of spines; tip of neurochaetae distinctly falcate. Neuropodial supra-acicular process thick, stout.

Description (based on syntypes of H. benthaliana (juveniles), except for number of elytra and segments, cf. Fauvel 1913).

Body with up to 39 segments. At anterior end ( Fig. 12A ), prostomium bilobed, with blunt cephalic peaks; ceratophore of median antenna in anterior notch, lateral antennae inserted ventrally, styles of antennae papillate, tapering; anterior pair of eyes situated dorsolaterally at widest part of prostomium, posterior pair dorsally near hind margin of prostomium; palps papillate, tapering.

Tentaculophores inserted laterally to prostomium, each with a dorsal and ventral tentacular cirrus, styles of cirri papillate, tapering (notochaetae indistinct). Second segment with first pair of elytra, biramous parapodia, and long buccal cirri. Following segments with tapering, short ventral cirri.

Fifteen pairs of elytra, covering dorsum, on segments 2, 4, 5, 7, then on every second segment to 23, 26, 29, 32; last seven segments cirrigerous; elytral margin smooth; conical microtubercles present in a patch near anterior margin ( Fig. 12B ). Cirrigerous segments with distinct dorsal tubercles; dorsal cirri with cylindrical cirrophore, style papillate, tapering.

Parapodia biramous; notopodia with elongate acicular lobe; neuropodia with elongate prechaetal acicular lobe with thick, stout supra-acicular process; neuropodial postchaetal lobe shorter than prechaetal lobe, rounded; tips of noto- and neuroacicula penetrating epidermis ( Fig. 12C ). Noto- and neurochaetae with faint rows of spines; tip of notochaetae blunt; tip of neurochaetae distinctly falcate, mainly bidentate with small secondary tooth (often abraded) ( Fig 12D,E ).

Measurements. Syntypes of H. benthaliana, BMNH 1885.12.1.75: 1 cs, juvenile, cut in two, L 6 mm, W 2.5 mm for 28 segments; 1 af ( Fig. 12A ), juvenile, L 5 mm, W 2.5 mm for 24 segments. Large syntype of H. joubini rosaurae, BMNH 1941.1.1.16–19: cs, L 17 mm, W 6 mm for 37 segments.

Remarks. Although the description of Harmothoe benthaliana is based on juveniles, the diagnostic characters can also be observed in adult specimens, like those of H. joubini rosaurae .

Harmothoe benthaliana and H. longisetis ( Grube, 1863) have similar elytra, but they differ mainly due to their chaetae; i.e. faint rows of spines and tip of neurochaetae distinctly hooked in H. benthaliana and distinct rows of spines and tip of neurochaetae straight to slightly bent in H. longisetis . Moreover the neuropodial supra-acicular process is slender digitiform in the latter and thick, stout in the former.

Distribution. Deep North Atlantic.

Habitat. Muddy sediments, in 1300–2275 m.

Figures

FIGURE 4. Identification characters of Harmothoe pokoui, H. bellani, H. evei, H. benthaliana, and H. longisetis.

FIGURE 12. Harmothoe benthaliana (syntype, af with 24 segments, BMNH 1885.12.1.75). (A) anterior end; right palp and styles of left and right dorsal tentacular cirri, and right dorsal cirrus missing; right parapodium of segment 2 cut off; (B) left elytron from unknown segment, modified after McIntosh (1885, pl. 20 fig. 7); (C) right parapodium from unknown segment, free in vial, posterior view, style of ventral cirrus missing; (D) long notochaeta; (E) middle neurochaeta. (Scales: A = 1 mm; B = 500 µm; C = 250 µm, D, E = 50 µm).